.a_main {
    font-size: large;
    display: block;
    float: left;
    text-decoration: none;
    border-radius: 5px;
    border: 2px solid;
    padding: 5px;
    margin: 5px;
}

.a_main:active {
    background: rgba(0, 255, 0, 1);
}

.a_main:hover {
    background-color: #0099E5;
}